Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known foil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The size, shape, and weight of rotor blades are factors that contribute to energy efficiencies of wind turbines. An increase in rotor blade size increases the energy production of a wind turbine, while a decrease in weight also furthers the efficiency of a wind turbine. Furthermore, as rotor blade sizes grow, extra attention needs to be given to the structural integrity of the rotor blades. Presently, large commercial wind turbines in existence and in development are capable of generating from about 1.5 to about 12.5 megawatts of power. These larger wind turbines may have rotor blade assemblies larger than 90 meters in diameter. Additionally, advances in rotor blade shape encourage the manufacture of a forward swept-shaped rotor blade having a general arcuate contour from the root to the tip of the blade, providing improved aerodynamics. Accordingly, efforts to increase rotor blade size, decrease rotor blade weight, and increase rotor blade strength, while also improving rotor blade aerodynamics, aid in the continuing growth of wind turbine technology and the adoption of wind energy as an alternative energy source.
As the size of wind turbines increases, particularly the size of the rotor blades, so do the respective costs of manufacturing, transporting, and assembly of the wind turbines. The economic benefits of increased wind turbine sizes must be weighed against these factors. For example, the costs of pre-forming, transporting, and erecting a wind turbine having rotor blades in the range of 90 meters may significantly impact the economic advantage of a larger wind turbine.
One known strategy for reducing the costs of pre-forming, transporting, and erecting wind turbines having rotor blades of increasing sizes is to manufacture the rotor blades in blade segments. The blade segments may be assembled to form the rotor blade after, for example, the individual blade segments are transported to an erection location. Further, in many cases where increased rotor blade sizes are desired, it may be desirable to increase the lengths of existing rotor blades. For example, an existing rotor blade may be divided into segments, and an insert may be provided between neighboring segments to increase the length of the segments.
In particular, one known method for joining rotor blade segments is through scarfing of neighboring blade segments to create tapered or angled joint faces on the blade segments. An insert may then be provided between the blade segments having mating joint faces. The joint faces may be joined together to create scarf joints, connecting the neighboring blade segments and insert. However, known methods and apparatus for scarfing rotor blade segments may have a variety of disadvantages. For example, a key factor in creating a strong scarf joint is the geometry of the mating joint faces. Scarf joints created in rotor blade segments must thus account for both the desired scarf angle and the curvature of the rotor blade segment. One current approach to scarfing a rotor blade segment is to manually grind a surface of the rotor blade to the desired angle. However, such manual approaches are inaccurate, leading to relatively weaker scarf joints, and are further time-consuming and thus costly. Other current approaches to scarfing rotor blade segments require the use of CNC machines. However, such approaches require prohibitively high capital costs, and are complex to program to adapt to the requirements of individual rotor blade segments.
Accordingly, improved methods and apparatus for scarfing rotor blade segments are desired in the art. In particular, methods and apparatus that accurately account for desired scarf angles and rotor blade segment curvatures would be advantageous. Further, methods and apparatus that provide such accuracy efficiently and at relatively low costs would be desired.